1. Field of the Invention
The present invention relates to a semiconductor device including a semiconductor element with a protection circuit and its testing method.
2. Description of Related Art
In a prior art semiconductor device including a semiconductor element so-called a gate-insulating-type transistor such as a power MOS transistor and an insulated gate bipolar transistor (IGBT), if an excessive voltage is applied to the gate of the gate-insulating-type transistor, the gate insulating layer thereof would be electrostatically destroyed. Therefore, in order to prevent the gate insulating layer from being electrostatically destroyed, a protection circuit is connected between the gate and source of the gate-insulating-type transistor to clamp the difference in voltage thereof.
The protection circuit is constructed by one or more diodes, and has an anode connected to an anode pad and a cathode connected to a source pad of the gate-insulating-type transistor. The anode pad is connected by a bonding wire to a gate pad of the gate-insulating-type transistor. On the other hand, in order to remove semiconductor devices with low gate breakdown voltages, a gate breakdown voltage test operation is carried out in a wafer state before bonding the bonding wire. In this case, a predetermined test voltage is applied to the gate of a gate-insulating-type transistor to determine whether or not the gate-insulating-type transistor is normally operated.
The above-described prior art semiconductor device is disclosed in Japanese Unexamined Patent Publication (Kokai) No. P2005-175054 A. This will be explained later in detail.
However, the inventor has recognized that, since the anode pad whose size is very large, is required for the protection circuit, the above-described prior art semiconductor device becomes large in size, which would increase the manufacturing cost.